I think "IN" and "OUT" markers is the best solution.
Better than any other graphical guideline that doesn't resort to blatant text?
Better than whatever is language-independent?
Better than icons that aren't mere arrows?
Better than idling animations?
If text, the antithesis of pattern recognition, were really the best option in such a visual game, that would be a huge red flag that the entire teleporter feature sucks. I hope the feature has merit.
come up with a uniform appearance
or use markers so that teleporters and receivers are always identifiable, and distinguishable
a lot of people would be very unhappy with [uniform appearance]
If "uniform appearance" means that there is only one gadget, and tilesets can't design their own: Agree that people would rage.
If "uniform appearance" means that there is a commonly-agreed-upon graphical feature (not icon) that all teleporters share (all exits have steps and torches, all teleporters have...?), and, likewise, that there is a second, different, commonly-agreed-upon graphical feature that all receivers share, then people wouldn't rage, instead we would have a great solution.
If "markers" mean slapped-on text, it's ugly. If "markers" means these commonly-agreed-upon graphical features, again you have a great idea.
The trouble with mirroring the sprites to distinguish a turning teleporter is that the player doesn't know which one is mirrored and which is normal; it has to be learned separately for every single type of teleporter. (And several of them are symmetrical....)
Agree, the turning remains hard to explain. Might fall back to icons tacked on top of the gadget, either by engine or by a second graphic?
-- Simon